From Team 449 Wiki
Wires enable the transfer of electricity from one device to another. They are used to power electric components and to send signals.
The size of a wire is measured using the American wire gauge (AWG) system. A smaller number indicates a thicker wire while a larger number indicates a thinner wire. The size of a wire can be found on the insulation, generally preceded by AWG. The size is necessary in order to correctly strip the wire and because different parts of the board require different sized wires. If the size cannot be read, estimate it using a wire stripper.
Pulse Width Modulation (usually just called PWM) wires are connected to the NI roboRIO and are gauge 20-28 generally. Normally 3 wires are crimped together (one black, one red, and one white) and placed in a housing with the red wire in the middle. The black wire is ground, the red is power, and the white is signal. Symbols on the roboRIO indicate which sides ground and signal should be placed.
Though this is bad practice, these cables are used to connect crimped terminals directly to a battery. They are used most often to run compressors or motors for the purpose of quickly testing a mechanism without the need for a full electronics board with motor controllers.